Abstract

Records of the response to strong ground shaking provide the best source
of information on the behavior of large structures during potentially damaging
excitations. Since the dynamic properties of many structures are markedly
different during response to strong ground motion than in small amplitude
ambient and forced vibration tests, it is important to extract as much information
as possible from the strong motion data.
Limitations in analyses using trial-and-error adjustment of the parameters
of a synthesized model, and similar limitations in the use of typical
transfer function approaches in the frequency domain, have recently led to
the development of systematic techniques of structural identification.[1]
Two such techniques for determining linear models of structures from their
recorded earthquake excitation and response are described herein, together
with the results of their application to the earthquake response of some
multi-story buildings. [2,3]
One approach is based upon achieving a best match of the time histories
of the calculated and recorded responses, while the other is a frequency
domain method which matches the Fourier transforms of the calculated and
recorded acceleration responses. It is possible either to determine a
single linear model appropriate for the entire response, or, by considering
segments of the records, to trace the changes of the effective linear
parameters with a series of models which approximate the non-linear and
time-varying behavior of the buildings.